Tuesday, May 27, 2008

SQL Teaser uniqueidentifier

Create this table

CREATE TABLE #bla (SomeVal uniqueidentifier)
INSERT #bla VALUES('D903D52D-DBFA-4904-9D95-F265152A391F')

what do you think this will return?

WHERE SomeVal = 'D903D52D-DBFA-4904-9D95-F265152A391F12345678910'
WHERE SomeVal = 'D903D52D-DBFA-4904-9D95-F265152A391F1'


What about this?

WHERE SomeVal = CONVERT(uniqueidentifier,'D903D52D-DBFA-4904-9D95-F265152A391F12345678910')

Interview With Erland Sommarskog About SQL Server and Transact SQL

I have interviewed Erland Sommarskog, you can find that interview here: Interview With Erland Sommarskog About SQL Server and Transact SQL


Wednesday, May 21, 2008

I have a question for you on DB development blunders!

Last week Kalen Delaney wrote Did You Know? I have a question for you on DBA Blunders! I though the comments were very interesting, S we did the DBA part but what about developers? What are some of the worst blunders you have seen?

Here are a couple of things

Starting a begin tran, then some insert/update command, never commiting but minimizing the window.

Here is my all time favorite, can you reduce this by 90%?

@Token int
@Token = 51234567

declare @val int

left(@Token,1) = 1
select @val = 1
else if left(@Token,1) = 2
select @val = 2
else if left(@Token,1) = 3
select @val = 3
else if left(@Token,1) = 4
select @val = 4
else if left(@Token,1) = 5
select @val = 5
else if left(@Token,1) = 6
select @val = 6
else if left(@Token,1) = 7
select @val = 7
else if left(@Token,1) = 8
select @val = 8
else if left(@Token,1) = 9
select @val = 9
else if left(@Token,1) = 0
select @val = 0

select @val

Actually we put that on the whiteboard after we found it in our code and every time the developer wanted something we teased him about it...Oh you mean like that (pointing to the whiteboard)

What about changing the datatype from smallint to int in the table but keeping the params smallint in the proc.....mmmm why do I get a conversion in the execution plan?

So let's here some of what you have seen others write, we all know we couldn't write stuff like that ourselves right? :-)

Monday, May 19, 2008

Spring Cleaning, Getting Rid Of Some Books

I did some spring cleaning yesterday, I got rid of some old or obsolete books. I asked some people at work if they want any of these books and I believe all the books except for the JCL book are about to be given away.

I got rid of these books because:
I got a new version
I don't use the technology anymore
The book is obsolete

Click on the image and you can see a bigger version on my flickr page.

Spring Cleaning

Thursday, May 08, 2008

SSMS Tools PACK 1.0 is now available

Mladen Prajdić just released SSMS Tools PACK 1.0. SSMS Tools PACK is an Add-In (Add-On) for Microsoft SQL Server Management Studio and Microsoft SQL Server Management Studio Express.

Here are some of the features

Uppercase/Lowercase keywords.
Run one script on multiple databases.
Copy execution plan bitmaps to clipboard.
Search Results in Grid Mode and Execution Plans.
Generate Insert statements for a single table, the whole database or current resultsets in grids.
Query Execution History (Soft Source Control).
Text document Regions and Debug sections.
Running custom scripts from Object explorer's Context menu.
CRUD (Create, Read, Update, Delete) stored procedure generation.
New query template.

Check it out here: http://www.ssmstoolspack.com/Main.aspx

How to log when a function is called?

This question came up today and here is one way of doing it. It requires running xp_cmdshell so this is probably not such a good idea.
The problem with functions is that you cannot just insert into any table. INSERT, UPDATE, and DELETE statements modifying table variables local to the function.
EXECUTE statements calling an extended stored procedures are allowed.
So with this in mind we know that we can call xp_cmdshell, from xp_cmdshell we can use osql
Let's take a look
We will be using tempdb

--Create the table
USE tempdb
CREATE TABLE LogMeNow (SomeValue varchar(50), SomeDate datetime default getdate())

--Here is the proc
LogMeNow (SomeValue) VALUES(@SomeValue)

--And here is the function
CREATE FUNCTION fnBla(@id int)
@SQL varchar(500)
SELECT @SQL = 'osql -S' +@@servername +' -E -q "exec tempdb..prLog ''fnBla''"'
EXEC master..xp_cmdshell @SQL

Now call the function a couple of times

SELECT dbo.fnBla(2)
SELECT dbo.fnBla(4)

And look inside the table


What if you were to run this?

SELECT dbo.fnBla(4),* FROM sys.sysobjects

See the problem? The function will be called for every row, if you have a big table this can be problematic!!!!!!!!

I tested this on SQL 2000 and on SQL 2005(including a named instance). So there you have it, this is one way. does it smell kludgy and do I feel somewhat dirty now? yes it does indeed :-(


Without running this what do you think will be printed?

@ int
@ =6
PRINT 'yes'
PRINT 'no'
PRINT @@rowcount

Wednesday, May 07, 2008


I was asked by a developer at work the other day why SQL Server does not have the create or replace syntax. I started thinking and there were some advantages and one big disadvantage

First the advantages

When scripting out a database you don’t have to generate if exists.....drop statements

When modifying an object from a file in source control you don’t have to change back and forth between CREATE and ALTER. This is really annoying sometimes; usually you create a proc or script out a proc and store it in Subversion/SourceSafe. Now you take that file, make some changes to the proc and run it. Of course it will tell you that the proc already exists, in general you don’t want to drop the proc and then execute the CREATE proc statement because then you have to worry about the permissions.(not everyone is running as dbo you know)

I can overwrite a proc without even knowing it. What if we both are working on a proc and somehow we pic the same name I create my proc, you work in a remote location, you create yours and mine is gone.

Of course it is all what you are used to, I am sure the Oracle guys are not overwriting each other’s procs every day either

So what do you think? Would you be in favor of this syntax or not? Can you think of more advantages or disadvantages?

Tuesday, May 06, 2008

What Would You Like To Ask Erland Sommarskog?

In the Who do you want to see interviewed next?(sqlblog) and Who do you want to see interviewed next?(here) blog post I asked for some names of people who YOU would like to see interviewed. Erland Sommarskog's name was submitted in comments a couple of times. I contacted Erland and am happy to anounce that he has agreed to do this.

The first time I heard of Erland Sommarskog was in the SQL Server programming newsgroups. I also read all the articles on his site. When I answer questions I usually give the link out to these 4 articles
Arrays and Lists in SQL Server
Implementing Error Handling with Stored Procedures
Error Handling in SQL Server – a Background
and of course The curse and blessings of dynamic SQL

I always wondered why he didn't write a SQL book. Hey, now I can ask him that :-)

Before you think of any questions please visit Erland's page first (http://www.sommarskog.se/index.html) and read some of the articles he wrote.

You can submit questions until Monday May 12th and then I will forward the questions to Erland.

What Would You Like To Ask Craig Freedman?

In the Who do you want to see interviewed next?(sqlblog) and Who do you want to see interviewed next?(here) blog post I asked for some names of people who YOU would like to see interviewed. Craig Freedman's name was submitted in comments a couple of times. I contacted Craig and am happy to anounce that he has agreed to do this.

Before you think of any questions please visit Craig's blog first(http://blogs.msdn.com/craigfr/) to get a feel of what kind of questions to ask. It would make sense to keep the questions focused on query processing, query execution, and query plans. I told Craig that if he doesn't like a question that he does not have to answer it.

You can submit questions until Monday May 12th and then I will forward the questions to Craig

Do you depend on sp_depends (no pun intended)

HTML Source EditorWord wrap I answered this question on the MSDN forums: How can I search all my sprocs to see if any use a function?
Several people suggested using sp_depends. You can't really depend on sp_depends because of deferred name resolution. Take a look at this

First create this proc

PROC SomeTestProc

now create this function

FUNCTION somefuction(@id int)
@id = 1

now run this


result: Object does not reference any object, and no objects reference it.

Most people will not create a proc before they have created the function. So when does this behavior rear its ugly head? When you script out all the objects in a database, if the function or any objects referenced by an object are created after the object that references them then sp_depends won't be 100% correct

SQL Server 2005 makes it pretty easy to do it yourself



FROM information_schema.routines


object_definition(object_id(specific_name)) LIKE '%somefuction%'


routine_type = 'procedure'

BTW somefuction is not a type, I already had a somefunction but was too lazy to change more than one character

Friday, May 02, 2008

Testing for SQL Server Vulnerabilities

I found this SQL Server Testing (not unit but vulnerability) page and decided I would post a link to it since it has some useful stuff. The link is below


Here is what is covered. Enjoy (or live in fear over the weekend)

1 Brief Summary
2 Short Description of the Issue
3 Black Box testing and example
3.1 SQL Server Peculiarities
3.2 Example 1: Testing for SQL Injection in a GET request.
3.3 Example 2: Testing for SQL Injection in a GET request (2).
3.4 Example 3: Testing in a POST request
3.5 Example 4: Yet another (useful) GET example
3.6 Example 5: custom xp_cmdshell
3.7 Example 6: Referer / User-Agent
3.8 Example 7: SQL Server as a port scanner
3.9 Example 8: Upload of executables
3.10 Obtain information when it is not displayed (Out of band)
3.11 Blind SQL injection attacks
3.11.1 Trial and error
3.11.2 In case more than one error message is displayed
3.11.3 Timing attacks
3.11.4 Checking for version and vulnerabilities
3.12 Example 9: bruteforce of sysadmin password
4 References

Thursday, May 01, 2008

Who do you want to see interviewed next?

I have interviewed a bunch of people already, some of them on this blog and some of them on SQLBlog

Below is the list of all the people so far

Louis Davidson
Itzik Ben-Gan
Ken Henderson
Kalen Delaney
Adam Machanic
Interview With Stéphane Faroult About Refactoring SQL Applications
Database Refactoring Interview With Scott W. Ambler
Interview With Joe Celko About The Forthcoming Book Thinking In Sets

Who else should I interview? I have some ideas but I would like you to participate. Here is my thinking, after we have a list of possible people, I will contact them and ask if they will agree to an interview. If they agree I will make a post here and ask you what you would like to ask this person. I usually have a good set of questions but there might be someone out there with some real good/interesting questions.
So post the name of the person you would like to see interviewed and hopefully this person will agree.

It would be nice if you did not pick a person who blogs at SQLBlog but if_you_really_wanted_to then I will not stop you :-0

Please keep it database related, it doesn't have to be specific to SQL Server but it has to be applicable to SQL Server.